JP2020088261A - Carbon concentration measurement method - Google Patents
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本発明は、シリコン単結晶中の炭素濃度を測定する方法に関する。 The present invention relates to a method for measuring carbon concentration in a silicon single crystal.
低温フォトルミネッセンス（ＰＬ）法による炭素濃度測定方法は、試料に電子線や炭素イオンまたは酸素イオンなどのイオンビーム（粒子線）を照射して複合欠陥を生成させ、その複合欠陥に起因するルミネッセンス強度を測定し、その強度から炭素濃度を定量する方法であり（例えば、非特許文献１、特許文献１）、ＦＴ−ＩＲ法やＳＩＭＳ法よりも、高感度で炭素濃度を定量できる方法である。
また、特許文献２〜４には、シリコン単結晶中の複合欠陥強度と炭素濃度の検量線を作成し、炭素濃度を定量する方法が開示されている。
The carbon concentration measuring method by the low temperature photoluminescence (PL) method is to irradiate a sample with an electron beam or an ion beam (particle beam) such as carbon ions or oxygen ions to generate a compound defect, and to generate a luminescence intensity caused by the compound defect. Is measured and the carbon concentration is quantified from the intensity thereof (for example, Non-Patent Document 1 and Patent Document 1), which is a method capable of quantifying the carbon concentration with higher sensitivity than the FT-IR method or the SIMS method.
Further, Patent Documents 2 to 4 disclose a method of quantifying the carbon concentration by creating a calibration curve of the composite defect strength and the carbon concentration in a silicon single crystal.
特許文献２には、シリコン単結晶に電子線を照射することで導入される格子間シリコン（Ｉ）由来のルミネッセンススペクトル（Ｗ線）をシリコン由来の発光線（ＴＯ線）で規格化した値と、シリコン単結晶中の炭素濃度の間で検量線を作成し、ルミネッセンス法で得られたＷ線／ＴＯ線から、炭素濃度を定量する方法が開示されている。
特許文献３には、シリコン単結晶中に炭素及び酸素以外のイオンを注入し、これにより発生する格子間炭素またはＧ線（Ｃｉ−Ｃｓ）、またはＣ線（Ｃｉ−Ｏｉ）のルミネッセンススペクトル強度と、炭素濃度の間で検量線を作成し、炭素関連複合欠陥のスペクトル強度から、炭素濃度を定量する方法が開示されている。
特許文献４には、シリコン単結晶に電子線を照射し、生成させたＧ線とＣ線の強度比と、シリコン単結晶中の炭素濃度と酸素濃度の濃度比の間で検量線を作成し、シリコン単結晶中の酸素濃度およびＧ線とＣ線の強度比から炭素濃度を測定する方法が開示されている。
In Patent Document 2, a luminescence spectrum (W line) derived from interstitial silicon (I) introduced by irradiating a silicon single crystal with an electron beam is standardized with a light emission line (TO line) derived from silicon. , A method for preparing a calibration curve between the carbon concentrations in a silicon single crystal and quantifying the carbon concentration from the W line/TO line obtained by the luminescence method is disclosed.
In Patent Document 3, an ion other than carbon and oxygen is injected into a silicon single crystal, and the interstitial carbon or G line (Ci-Cs) or C line (Ci-Oi) luminescence spectrum intensity generated by this is obtained. , A method of creating a calibration curve between carbon concentrations and quantifying the carbon concentration from the spectral intensity of carbon-related complex defects is disclosed.
In Patent Document 4, a calibration curve is created between the intensity ratio of G and C lines generated by irradiating a silicon single crystal with an electron beam and the concentration ratio of carbon concentration and oxygen concentration in the silicon single crystal. , A method for measuring the carbon concentration from the oxygen concentration in a silicon single crystal and the intensity ratio of the G line and the C line is disclosed.
前記したように、ＰＬ法による炭素濃度測定方法は数多く開示されている。しかし、いずれも炭素濃度が既知で、且つ炭素濃度が異なるシリコン単結晶を複数用意し、複合欠陥のルミネッセンス強度を測定し、炭素濃度との検量線を作成した後に、ようやく測定対象である測定サンプルの複合欠陥のルミネッセンス強度を測定し、これを前記検量線に当てはめることにより、シリコン単結晶中の炭素濃度を定量する方法である。 As described above, many carbon concentration measuring methods by the PL method have been disclosed. However, in each case, the carbon concentration is known, and a plurality of silicon single crystals having different carbon concentrations are prepared, the luminescence intensity of the complex defect is measured, and after creating a calibration curve with the carbon concentration, a measurement sample that is finally a measurement target Is a method of quantifying the carbon concentration in the silicon single crystal by measuring the luminescence intensity of the composite defect and applying the luminescence intensity to the calibration curve.
特に、シリコン単結晶中の酸素濃度、Ｇ線とＣ線の強度比（および比例定数）から炭素濃度を測定する炭素濃度測定にあたって、必要に応じて粒子線の照射量を調整してルミネッセンススペクトルのピーク強度を大きくする場合がある（例えば、特願２０１８−００３４２７）。しかし、このように粒子線照射量を変えた場合においても、改めて炭素濃度および酸素濃度が既知のサンプルを複数用意し、変更した粒子線照射量の下、特願２０１８−００３４２７のような新しい比例定数を求める煩雑な作業を行った後でないと炭素濃度を求める事ができないという問題がある。 In particular, when measuring the carbon concentration from the oxygen concentration in the silicon single crystal and the intensity ratio (and proportionality constant) of the G line and the C line, the dose of the particle beam is adjusted as necessary to measure the carbon concentration. The peak intensity may be increased (for example, Japanese Patent Application No. 2018-003427). However, even when the particle beam irradiation amount is changed in this way, a plurality of samples whose carbon concentration and oxygen concentration are known are prepared again, and under the changed particle beam irradiation amount, a new proportional ratio as in Japanese Patent Application No. 2018-003427 is obtained. There is a problem that the carbon concentration cannot be obtained unless complicated work for obtaining the constant is performed.
本発明は、上記従来技術の問題点に鑑みてなされたものであって、シリコン単結晶中の炭素濃度を簡便に測定する方法を提供することを目的とする。 The present invention has been made in view of the problems of the above-mentioned conventional techniques, and an object thereof is to provide a method for simply measuring the carbon concentration in a silicon single crystal.
上記目的を達成するために、本発明は、粒子線を照射したシリコン単結晶をＰＬ測定またはＣＬ測定して得られるＧ線強度およびＣ線強度と、別に求めた酸素濃度を用いて、前記シリコン単結晶中の炭素濃度を測定する炭素濃度測定方法であって、
前記シリコン単結晶中の炭素濃度を、下記式
炭素濃度＝比例定数×酸素濃度×（Ｇ線強度／Ｃ線強度）…（Ａ）
を用いて測定するとき、
予め、第１の粒子線照射条件における、前記式（Ａ）の前記比例定数である第１の比例定数α１を求めておき、
次に、シリコン単結晶のサンプルを用意し、
前記第１の比例定数α１を求めたときと同じ前記第１の粒子線照射条件でのＰＬ測定またはＣＬ測定を行い、Ｇ線強度Ｇ１およびＣ線強度Ｃ１を求め、かつ、
前記第１の粒子線照射条件とは異なる第２の粒子線照射条件でのＰＬ測定またはＣＬ測定を行い、Ｇ線強度Ｇ２およびＣ線強度Ｃ２を求め、
その後、前記第２の粒子線照射条件における、前記式（Ａ）の前記比例定数である第２の比例定数α２を、下記式
比例定数α２＝比例定数α１×｛（Ｇ線強度Ｇ１／Ｃ線強度Ｃ１）／（Ｇ線強度Ｇ２／Ｃ線強度Ｃ２）｝…（Ｂ）
から決定し、
該決定した比例定数α２を代入した前記式（Ａ）を用いて、前記第２の粒子線照射条件における、前記シリコン単結晶中の炭素濃度の測定を行うことを特徴とする炭素濃度測定方法を提供する。
In order to achieve the above object, the present invention uses the G-line intensity and C-line intensity obtained by PL measurement or CL measurement of a silicon single crystal irradiated with a particle beam, and the oxygen concentration obtained separately to obtain the above-mentioned silicon. A carbon concentration measuring method for measuring the carbon concentration in a single crystal,
The carbon concentration in the silicon single crystal is calculated by the following formula: carbon concentration=proportional constant×oxygen concentration×(G line intensity/C line intensity) (A)
When measuring with
In advance, the first proportionality constant α1 which is the proportionality constant of the formula (A) under the first particle beam irradiation condition is obtained,
Next, prepare a sample of silicon single crystal,
PL measurement or CL measurement under the same first particle beam irradiation condition as when the first proportionality constant α1 is obtained is performed to obtain a G ray intensity G1 and a C ray intensity C1, and
PL measurement or CL measurement under a second particle beam irradiation condition different from the first particle beam irradiation condition is performed to obtain a G ray intensity G2 and a C ray intensity C2,
Then, under the second particle beam irradiation condition, the second proportional constant α2, which is the proportional constant of the formula (A), is calculated by the following formula: proportional constant α2=proportional constant α1×{(G ray intensity G1/C ray Intensity C1)/(G line intensity G2/C line intensity C2)}... (B)
Decided from
A carbon concentration measuring method characterized in that the carbon concentration in the silicon single crystal is measured under the second particle beam irradiation condition by using the equation (A) in which the determined proportionality constant α2 is substituted. provide.
このような炭素濃度測定方法であれば、第２の比例定数α２を決定する際に、特願２０１８−００３４２７のように、用いるサンプルについて酸素濃度や炭素濃度を求め、さらにＰＬ測定等によるＧ線強度やＣ線強度を求めるといった煩雑な作業を行わなくても、第２の粒子線照射条件における第２の比例定数α２を簡便に精度良く求めることができる。
そして、該第２の比例定数α２を用いた式（Ａ）によって、第２の粒子線照射条件における、炭素濃度の測定を簡便かつ高精度で行うことができる。
With such a carbon concentration measuring method, when determining the second proportionality constant α2, as in Japanese Patent Application No. 2018-003427, the oxygen concentration and the carbon concentration of the sample to be used are obtained, and the G line by PL measurement or the like is further obtained. The second proportionality constant α2 under the second particle beam irradiation condition can be simply and accurately obtained without performing a complicated work such as obtaining the intensity and the C-ray intensity.
Then, by the formula (A) using the second proportional constant α2, the carbon concentration can be measured easily and highly accurately under the second particle beam irradiation condition.
このとき、前記第２の粒子線照射条件を、前記第１の粒子線照射条件から粒子線照射量のみを変えた条件とすることができる。 At this time, the second particle beam irradiation condition may be a condition in which only the particle beam irradiation amount is changed from the first particle beam irradiation condition.
このようにすれば、粒子線照射量以外の条件、例えば粒子線やその加速電圧などは変えないので、より高い精度で第２の比例定数α２を求めることができる。 By doing so, conditions other than the particle beam irradiation amount, for example, the particle beam and its accelerating voltage are not changed, so that the second proportional constant α2 can be obtained with higher accuracy.
また、前記シリコン単結晶のサンプルとして、
１枚のシリコン単結晶ウェーハから、該シリコン単結晶ウェーハの中心から同じ距離の位置から採取した２つのウェーハ片を用意し、
前記第１の粒子線照射条件でのＰＬ測定またはＣＬ測定を前記２つのウェーハ片のうちの一方で行い、
前記第２の粒子線照射条件でのＰＬ測定またはＣＬ測定を他方で行うことができる。
In addition, as a sample of the silicon single crystal,
Two wafer pieces taken from one silicon single crystal wafer at the same distance from the center of the silicon single crystal wafer are prepared,
PL measurement or CL measurement under the first particle beam irradiation condition is performed on one of the two wafer pieces,
The PL measurement or CL measurement under the second particle beam irradiation condition can be performed on the other side.
このようにすれば、上記２つのウェーハ片の炭素濃度、酸素濃度は同一とみなせるので、第２の比例定数α２を決定する際、より確実に、用いたサンプルの炭素濃度、酸素濃度を求めることなく、式（Ｂ）により第２の比例定数α２を求めることが出来る。 By doing so, the carbon concentration and the oxygen concentration of the two wafer pieces can be regarded as the same, and therefore, when determining the second proportionality constant α2, the carbon concentration and the oxygen concentration of the sample used should be determined more reliably. Instead, the second proportional constant α2 can be obtained by the equation (B).
あるいは、前記第２の粒子線照射条件でのＰＬ測定またはＣＬ測定として、
前記第１の粒子線照射条件で粒子線を照射した前記シリコン単結晶のサンプルに、前記第１の粒子線照射条件の粒子線照射量と第２の粒子線照射条件の粒子線照射量の差分を追加照射して行うことができる。
Alternatively, as PL measurement or CL measurement under the second particle beam irradiation condition,
The difference between the particle beam irradiation amount under the first particle beam irradiation condition and the particle beam irradiation amount under the second particle beam irradiation condition for the sample of the silicon single crystal irradiated with the particle beam under the first particle beam irradiation condition. Can be additionally irradiated.
このようにすれば、第１の粒子線照射条件と第２の粒子線照射条件で粒子線を照射するサンプルは同じものであるので、第２の比例定数α２を決定する際、より確実に、用いたサンプルの炭素濃度、酸素濃度を求めることなく、式（Ｂ）により第２の比例定数α２を求めることが出来る。特に、第１の粒子線照射条件の粒子線照射量よりも第２の粒子線照射条件の粒子線照射量を増やしたい場合は、この方法が有効である。 By doing so, since the samples irradiated with the particle beam under the first particle beam irradiation condition and the second particle beam irradiation condition are the same, when determining the second proportionality constant α2, the The second proportional constant α2 can be calculated by the equation (B) without calculating the carbon concentration and oxygen concentration of the sample used. This method is particularly effective when it is desired to increase the particle beam irradiation amount under the second particle beam irradiation condition more than the particle beam irradiation amount under the first particle beam irradiation condition.
このとき、前記第２の粒子線照射条件での粒子線照射量を、前記第１の粒子線照射条件の粒子線照射量の２〜１０倍、または０．１〜０．５倍とすることができる。 At this time, the particle beam irradiation amount under the second particle beam irradiation condition is 2 to 10 times, or 0.1 to 0.5 times the particle beam irradiation amount under the first particle beam irradiation condition. You can
前述したように、第１の粒子線照射条件の照射量が最適でなかった場合、照射量を増やしたり、減らしたりする必要性が生じる場合がある。第１の粒子線照射条件が通常使用している条件の場合、既に予備実験などである程度適切な条件となっているため、第２の粒子照射条件で例えば照射量を増やす場合は２〜１０倍の照射量で十分である。また、逆に照射量を減らす場合も、０．１〜０．５倍の照射量で十分である。 As described above, when the dose of the first particle beam irradiation condition is not optimal, it may be necessary to increase or decrease the dose. In the case where the first particle beam irradiation condition is the condition that is normally used, it is already a suitable condition to some extent in a preliminary experiment, and therefore, when the irradiation amount is increased in the second particle irradiation condition, for example, 2 to 10 times. Is sufficient. On the contrary, when the irradiation dose is reduced, the irradiation dose of 0.1 to 0.5 times is sufficient.
また、前記測定するシリコン単結晶中の炭素濃度を、１×１０１３ａｔｏｍｓ／ｃｍ３以上とすることができる。 Further, the carbon concentration in the silicon single crystal to be measured can be 1×10 13 atoms/cm 3 or more.
このように本発明の測定方法であれば、１×１０１３ａｔｏｍｓ／ｃｍ３という低濃度の炭素濃度を簡便に精度良く求めることが可能となる。 As described above, according to the measuring method of the present invention, a low carbon concentration of 1×10 13 atoms/cm 3 can be easily and accurately obtained.
以上のように、本発明の炭素濃度測定方法であれば、第２の比例定数を決定する際に、特願２０１８−００３４２７のような、用いるサンプルの炭素濃度と酸素濃度の測定など煩雑な作業を行わなくても、第２の粒子線照射条件における第２の比例定数α２を簡便に精度良く求めることができる。そして、該第２の比例定数α２を用いた式（Ａ）を用いることで、第２の粒子線照射条件における、炭素濃度の測定を簡便かつ高精度で行うことができる。 As described above, according to the carbon concentration measuring method of the present invention, when determining the second proportional constant, complicated work such as measurement of carbon concentration and oxygen concentration of a sample to be used, as in Japanese Patent Application No. 2018-003427, is performed. Without performing the above, the second proportionality constant α2 under the second particle beam irradiation condition can be simply and accurately obtained. Then, by using the formula (A) using the second proportional constant α2, the carbon concentration can be measured easily and highly accurately under the second particle beam irradiation condition.
以下、本発明について図面を参照して実施の形態を説明するが、本発明はこれに限定されるものではない。
前述したように、式（Ａ）、すなわち、
炭素濃度＝比例定数×酸素濃度×（Ｇ線強度／Ｃ線強度）…（Ａ）
を用いて炭素濃度を求める際に、予め比例定数を決定する必要があり、様々な条件を検討して粒子線の種類やその照射量を決定し、決定した条件で酸素濃度及び炭素濃度の異なるサンプルに粒子線を照射し、得られたＧ線強度、Ｃ線強度及び各サンプルの炭素濃度、酸素濃度から式（Ａ）の比例定数を決定していた。
Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.
As mentioned above, equation (A), that is,
Carbon concentration = proportional constant x oxygen concentration x (G line intensity/C line intensity) (A)
When determining the carbon concentration using, the proportional constant must be determined in advance, and various conditions are examined to determine the type of particle beam and its irradiation dose, and the oxygen concentration and carbon concentration differ depending on the determined conditions. The sample was irradiated with a particle beam, and the proportional constant of the formula (A) was determined from the obtained G ray intensity, C ray intensity, and the carbon concentration and oxygen concentration of each sample.
このように、式（Ａ）を用いてシリコン単結晶中の炭素濃度を求めていく中で、Ｇ線、Ｃ線のどちらか一方、または両方のピークが弱く、照射量を増やしてピーク強度を大きくする必要性が生じる場合がある。逆に、決定した照射量が強すぎて、シリコン単結晶の構造が乱れてピークが弱くなっている場合もあり、この場合は照射量を減らしてピーク強度を大きくする必要性が生じる場合がある。 As described above, when the carbon concentration in the silicon single crystal is calculated using the formula (A), one or both peaks of the G line and the C line are weak, and the irradiation amount is increased to increase the peak intensity. It may be necessary to make it larger. On the contrary, the determined dose may be too strong, and the structure of the silicon single crystal may be disturbed to weaken the peak. In this case, it may be necessary to reduce the dose and increase the peak intensity. .
しかし、粒子線の照射量を変えると、式（Ａ）において、照射量変更前に用いていた比例定数を用いることができなくなり、新たな比例定数を決定するために、照射量変更前の比例定数を決定したときと同様の煩雑な作業を必要としていた。 However, if the dose of the particle beam is changed, the proportional constant used before the dose change cannot be used in the formula (A), and in order to determine a new proportional constant, the proportional constant before the dose change The same complicated work as when determining the constant was required.
そこで本発明者は鋭意研究を行ったところ、粒子線照射量変更前における比例定数（第１の粒子線照射条件における第１の比例定数α１）と、照射量変更後における比例定数（第２の粒子線照射条件における第２の比例定数α２）との関係式を用いることにより、特願２０１８−００３４２７のような煩雑な作業を行わなくても、精度の高い第２の粒子線照射条件における第２の比例定数α２を求めることができることを見出した。なお、本発明者が導き出したその関係式は以下の通りである。
比例定数α２＝比例定数α１×｛（Ｇ線強度Ｇ１／Ｃ線強度Ｃ１）／（Ｇ線強度Ｇ２／Ｃ線強度Ｃ２）｝…（Ｂ）
そして、さらにこの第２の比例定数α２を用いた式（Ａ）により、第２の粒子線照射条件における炭素濃度の測定を簡単に行うことができることを見出し、本発明を完成させた。
Then, the present inventor has conducted diligent research and found that the proportional constant before changing the particle beam irradiation amount (first proportional constant α1 under the first particle beam irradiation condition) and the proportional constant after changing the irradiation amount (second By using the relational expression with the second proportionality constant α2) under the particle beam irradiation condition, it is possible to obtain the first value under the highly accurate second particle beam irradiation condition without performing complicated work such as Japanese Patent Application No. 2018-003427. It was found that the proportional constant α2 of 2 can be obtained. The relational expression derived by the present inventor is as follows.
Proportional constant α2=proportional constant α1×{(G line intensity G1/C line intensity C1)/(G line intensity G2/C line intensity C2)}...(B)
Further, they have found that the carbon concentration under the second particle beam irradiation condition can be easily measured by the formula (A) using the second proportionality constant α2, and have completed the present invention.
図１に本発明の炭素濃度測定方法の工程の一例を示す。
（工程１：第１の比例定数α１の決定）
まず、粒子線（電子線やイオンビーム）を照射したシリコン単結晶の比例定数決定用サンプルをＰＬ測定して得られるＧ線強度［ａ．ｕ．］、Ｃ線強度［ａ．ｕ．］、および別に求めた炭素濃度［ａｔｏｍｓ／ｃｍ３］、酸素濃度［ｐｐｍａ−ＪＥＩＴＡ］を用いて、
炭素濃度＝比例定数×酸素濃度×（Ｇ線強度／Ｃ線強度）…（Ａ）
となる比例定数をあらかじめ求めておく。
なお、本発明の炭素濃度測定方法の工程を説明するにあたってＰＬ法を用いる例を挙げるが、代わりにＣＬ（カソードルミネッセンス）法を用いることもできる。
FIG. 1 shows an example of steps of the carbon concentration measuring method of the present invention.
(Step 1: Determination of the first proportionality constant α1)
First, the G-ray intensity obtained by PL measurement of a sample for determining a proportional constant of a silicon single crystal irradiated with a particle beam (electron beam or ion beam) [a. u. ], C line intensity [a. u. ], and the carbon concentration [atoms/cm 3 ] and oxygen concentration [ppma-JEITA], which are separately obtained,
Carbon concentration = proportional constant x oxygen concentration x (G line intensity/C line intensity) (A)
The proportional constant that becomes
An example of using the PL method will be described in describing the steps of the carbon concentration measuring method of the present invention, but a CL (cathode luminescence) method can be used instead.
具体的には、炭素濃度、および酸素濃度が異なるシリコン単結晶基板（比例定数決定用サンプル）を１５水準用意する。このとき、導出される比例定数の精度を上げる為、５水準以上用意することが好ましい。
そして、これらのサンプルの炭素濃度、および酸素濃度をＳＩＭＳ法（あるいはＦＴ−ＩＲ法など）で測定する。その後、電子線照射装置により各シリコン単結晶基板に２ＭＶの加速電圧で１．０×１０１５ｅｌｅｃｔｒｏｎｓ／ｃｍ２の電子線を照射する。これらの条件を第１の粒子線照射条件とする。こうして、シリコン単結晶基板にＧ線、およびＣ線を形成させ、それらのピーク強度をＰＬ法で測定する。なお、このときのサンプル温度は液体ヘリウム温度とする。
Specifically, 15 levels of silicon single crystal substrates (samples for determining a proportional constant) having different carbon concentrations and oxygen concentrations are prepared. At this time, it is preferable to prepare five or more levels in order to improve the accuracy of the derived proportional constant.
Then, the carbon concentration and oxygen concentration of these samples are measured by SIMS method (or FT-IR method or the like). Then, each silicon single crystal substrate is irradiated with an electron beam of 1.0×10 15 electrons/cm 2 at an accelerating voltage of 2 MV by an electron beam irradiation device. These conditions are the first particle beam irradiation conditions. Thus, the G line and the C line are formed on the silicon single crystal substrate, and their peak intensities are measured by the PL method. The sample temperature at this time is the liquid helium temperature.
これらシリコン単結晶基板において、得られた炭素濃度、酸素濃度、Ｇ線強度、およびＣ線強度を上記の式（Ａ）に代入し、得られた比例定数の平均値を第１の比例定数α１とする。このようにして、第１の比例定数α１として４．４５×１０１４ａｔｏｍｓ／（ｃｍ３・ｐｐｍａ）が得られた。
なお、上記の第１の粒子線照射条件および第１の比例定数α１は一例であって、当然、これらの条件や数値に限定されるものではなく、適宜決定することができる。
In these silicon single crystal substrates, the obtained carbon concentration, oxygen concentration, G ray intensity, and C ray intensity were substituted into the above formula (A), and the average value of the obtained proportional constants was calculated as the first proportional constant α1. And In this way, 4.45×10 14 atoms/(cm 3 ·ppma) was obtained as the first proportionality constant α1.
The above-mentioned first particle beam irradiation condition and the first proportionality constant α1 are merely examples, and needless to say, are not limited to these conditions and numerical values, and can be appropriately determined.
（工程２：第２の比例定数α２の決定）
上記のようにして第１の粒子線照射条件における第１の比例定数α１を決定した後は、通常、実際の炭素濃度測定対象のシリコン単結晶に対して第１の粒子線照射条件で粒子線を照射して得たＧ線強度、Ｃ線強度、別に求めた酸素濃度、第１の比例定数α１を式（Ａ）に代入して炭素濃度を求めることができる。
(Step 2: Determination of second proportionality constant α2)
After the first proportionality constant α1 under the first particle beam irradiation condition is determined as described above, the particle diameter of the silicon single crystal whose carbon concentration is actually measured is usually measured under the first particle beam irradiation condition. The carbon concentration can be obtained by substituting the G-line intensity and the C-line intensity obtained by irradiating with, the oxygen concentration obtained separately, and the first proportional constant α1 into the formula (A).
しかしながら、前述したように、第１の粒子線照射条件でのＧ線などの強度測定において粒子線の照射量を調整する必要が生じる場合がある。粒子線の照射量を増やせば、もしくは減らせば、より低濃度の炭素濃度を定量することができる場合がある。この場合、特願２０１８−００３４２７のように、粒子線の照射量を変えた比例定数決定用サンプルを用意し、上記と同様の煩雑な方法を行えば、照射量変更後の条件に対応する比例定数を求めることが出来るが、サンプルの炭素濃度や酸素濃度を求める必要がある。 However, as described above, it may be necessary to adjust the dose of the particle beam in the measurement of the intensity of the G ray or the like under the first particle beam irradiation condition. It may be possible to quantify a lower carbon concentration by increasing or decreasing the particle beam irradiation dose. In this case, as in Japanese Patent Application No. 2018-003427, if a sample for determining a proportional constant in which the dose of particle beam is changed is prepared and a complicated method similar to the above is performed, the proportionality corresponding to the condition after the dose is changed. The constant can be calculated, but it is necessary to calculate the carbon concentration and oxygen concentration of the sample.
しかし、比例定数決定用サンプルの炭素濃度と酸素濃度が第１の粒子線照射条件と第２の粒子線照射条件で等しい場合、式（Ａ）をより詳細に検討した結果、次のことが明らかとなった。
第１の粒子線照射条件におけるＧ線強度、Ｃ線強度を、Ｇ１、Ｃ１とし、第２の粒子線照射条件におけるＧ線強度、Ｃ線強度を、Ｇ２、Ｃ２とすると、
炭素濃度＝比例定数α１×酸素濃度×（Ｇ線強度Ｇ１／Ｃ線強度Ｃ１）
＝比例定数α２×酸素濃度×（Ｇ線強度Ｇ２／Ｃ線強度Ｃ２）
であり、比例定数α２について解くと、下記式（Ｂ）となる。
比例定数α２＝比例定数α１×｛（Ｇ線強度Ｇ１／Ｃ線強度Ｃ１）／（Ｇ線強度Ｇ２／Ｃ線強度Ｃ２）…（Ｂ）
即ち、式（Ｂ）には炭素濃度、酸素濃度が含まれていないため、比例定数α１が分かっている場合には、特願２０１８−００３４２７のように、比例定数決定用のサンプルを用意し、該比例定数決定用サンプルの炭素濃度や酸素濃度をわざわざ測定することなく、比例定数α２を求めることが出来る。新たな第２の粒子線照射条件の下における新たな第２の比例定数α２を得る際に、従来のような煩雑な作業をなくして簡単かつ高精度に比例定数α２を求めることができる。
However, when the carbon concentration and the oxygen concentration of the sample for determining the proportionality constant are equal under the first particle beam irradiation condition and the second particle beam irradiation condition, as a result of a more detailed examination of the formula (A), the following fact is revealed. Became.
If the G-ray intensity and C-ray intensity under the first particle beam irradiation condition are G1 and C1, and the G-ray intensity and C-ray intensity under the second particle beam irradiation condition are G2 and C2,
Carbon concentration = proportional constant α1 x oxygen concentration x (G line intensity G1/C line intensity C1)
= Proportional constant α2 x oxygen concentration x (G line intensity G2/C line intensity C2)
Then, when the proportional constant α2 is solved, the following equation (B) is obtained.
Proportional constant α2=proportional constant α1×{(G line intensity G1/C line intensity C1)/(G line intensity G2/C line intensity C2)...(B)
That is, since the carbon concentration and the oxygen concentration are not included in the formula (B), when the proportional constant α1 is known, a sample for determining the proportional constant is prepared as in Japanese Patent Application No. 2018-003427. The proportional constant α2 can be obtained without the need to measure the carbon concentration and oxygen concentration of the proportional constant determining sample. When obtaining the new second proportional constant α2 under the new second particle beam irradiation condition, the proportional constant α2 can be obtained easily and highly accurately without the complicated work of the prior art.
以下、この第２の比例定数α２を決定する具体的な手順についてさらに詳述する。
シリコン単結晶のサンプルを用意し、第１の比例定数α１を求めたときと同じ第１の粒子線照射条件でのＰＬ測定またはＣＬ測定を行い、Ｇ線強度Ｇ１およびＣ線強度Ｃ１を求める。また、第１の粒子線照射条件とは異なる第２の粒子線照射条件でのＰＬ測定またはＣＬ測定を行い、Ｇ線強度Ｇ２およびＣ線強度Ｃ２を求める。
Hereinafter, a specific procedure for determining the second proportionality constant α2 will be described in more detail.
A sample of a silicon single crystal is prepared, PL measurement or CL measurement is performed under the same first particle beam irradiation condition as when the first proportionality constant α1 was obtained, and the G ray intensity G1 and the C ray intensity C1 are obtained. Further, PL measurement or CL measurement under the second particle beam irradiation condition different from the first particle beam irradiation condition is performed to obtain the G ray intensity G2 and the C ray intensity C2.
第１の粒子線照射条件や第２の粒子線照射条件自体は特に限定されず、適宜決定することができる。このとき、第２の粒子線照射条件は、第１の粒子線照射条件と、例えば粒子線の種類、加速電圧、照射量、入射角度が異なっていれば良い。
また、第１の粒子線照射条件は、先に挙げた例の他、通常行っている炭素濃度測定時と同様の条件とすることができる。
さらに、第２の粒子線照射条件は、第１の粒子線照射条件とは粒子線照射量のみが異なっていることがより好ましい。ここで第１の粒子線照射条件は、通常は既に予備実験などである程度適切な条件となっているため、特に第２の粒子線照射条件として第１の粒子線照射量のみを変更する場合は、第１の粒子線照射条件からの微調整であり、照射量を増やす場合は２〜１０倍の照射量から選べば十分である。照射量を減らす場合も同様で、０．１〜０．５倍の照射量から選べば十分である。
例えば、先に挙げた例のように第１の粒子線照射条件として１×１０１５ｅｌｅｃｔｒｏｎｓ／ｃｍ２の電子線を照射したとき、Ｇ線強度のピークが弱かった場合は、第２の粒子線照射条件として、電子線照射量を５×１０１５ｅｌｅｃｔｒｏｎｓ／ｃｍ２とすることができる。
The first particle beam irradiation conditions and the second particle beam irradiation conditions themselves are not particularly limited and can be appropriately determined. At this time, the second particle beam irradiation condition may be different from the first particle beam irradiation condition in terms of, for example, the type of particle beam, the acceleration voltage, the irradiation amount, and the incident angle.
Further, the first particle beam irradiation condition may be the same as the condition for the carbon concentration measurement which is usually performed, in addition to the above-mentioned examples.
Furthermore, it is more preferable that the second particle beam irradiation condition is different from the first particle beam irradiation condition only in the particle beam irradiation amount. Here, since the first particle beam irradiation condition is already a proper condition to some extent in a preliminary experiment or the like, especially when changing only the first particle beam irradiation amount as the second particle beam irradiation condition. It is fine adjustment from the first particle beam irradiation condition, and when increasing the irradiation amount, it is sufficient to select from the irradiation amount of 2 to 10 times. The same applies when reducing the irradiation dose, and it is sufficient to select from the irradiation dose of 0.1 to 0.5 times.
For example, when the electron beam of 1×10 15 electrons/cm 2 is irradiated as the first particle beam irradiation condition as in the above-mentioned example, and the peak of the G-ray intensity is weak, the second particle beam As the irradiation condition, the electron beam irradiation amount can be set to 5×10 15 electrons/cm 2 .
このように、第２の粒子線照射条件として、第１の粒子線照射条件から粒子線照射量のみを変えた条件とすれば、粒子線照射量以外の条件、例えば粒子線やその加速電圧などは変えないので、より高い精度で第２の比例定数α２を求めることができる。 In this way, if the second particle beam irradiation condition is a condition in which only the particle beam irradiation amount is changed from the first particle beam irradiation condition, conditions other than the particle beam irradiation amount, such as particle beam and its accelerating voltage Does not change, the second proportionality constant α2 can be obtained with higher accuracy.
ここで、シリコン単結晶の比例定数決定用サンプルの用意の仕方と、第１の粒子線照射条件や第２の粒子線照射条件下でのＰＬ測定等の仕方の例を挙げる。
まず、シリコン単結晶の比例定数決定用サンプルとして、１枚のシリコン単結晶ウェーハから、該シリコン単結晶ウェーハの中心から同じ距離の位置から採取した２つのウェーハ片を用意する。そして、第１の粒子線照射条件でのＰＬ測定を２つのウェーハ片のうちの一方で行い、Ｇ線強度Ｇ１とＣ線強度Ｃ１を求める。そして、第２の粒子線照射条件でのＰＬ測定を他方で行い、Ｇ線強度Ｇ２とＣ線強度Ｃ２を求める。
この方法であれば、用意した２つのウェーハ片の炭素濃度、酸素濃度は同一とみなすことができ、より確実に、式（Ｂ）により第２の比例定数α２を簡単に求めることができる。第２の比例定数α２を求める際に、特願２０１８−００３４２７のようにサンプルの炭素濃度および酸素濃度を別途測定する必要もないので簡便である。
Here, examples of a method of preparing a sample for determining a proportional constant of a silicon single crystal and a method of PL measurement under the first particle beam irradiation condition and the second particle beam irradiation condition will be given.
First, as a sample for determining a proportional constant of a silicon single crystal, two wafer pieces taken from one silicon single crystal wafer at the same distance from the center of the silicon single crystal wafer are prepared. Then, the PL measurement under the first particle beam irradiation condition is performed on one of the two wafer pieces, and the G ray intensity G1 and the C ray intensity C1 are obtained. Then, the PL measurement under the second particle beam irradiation condition is performed on the other side, and the G ray intensity G2 and the C ray intensity C2 are obtained.
According to this method, the prepared two wafer pieces can be regarded as having the same carbon concentration and oxygen concentration, and the second proportional constant α2 can be easily obtained more easily by the formula (B). When obtaining the second proportionality constant α2, it is not necessary to separately measure the carbon concentration and oxygen concentration of the sample as in Japanese Patent Application No. 2018-003427, which is simple.
別の例としては、シリコン単結晶のサンプルを１つ用意し、これに第１の粒子線照射条件で粒子線を照射してＰＬ測定を行い、Ｇ線強度Ｇ１とＣ線強度Ｃ１を求める。次に、この第１の粒子線照射条件で粒子線を照射したシリコン単結晶のサンプルに、第１の粒子線照射条件の粒子線照射量と第２の粒子線照射条件の粒子線照射量の差分を追加照射してＰＬ測定を行い、Ｇ線強度Ｇ２とＣ線強度Ｃ２を求める。
このような方法であれば、同一のサンプル使用のため、当然、炭素濃度および酸素濃度は同じであり、式（Ｂ）を用いて第２の比例定数α２を簡単に求めることができる。特に、第１の粒子線照射条件の粒子線照射量よりも第２の粒子線照射条件の粒子線照射量を増やしたい場合に有効な方法である。
逆に、第１の粒子線照射条件の粒子線照射量よりも第２の粒子線照射条件の粒子線照射量を減らしたい場合は、先に第２の粒子線照射条件でＰＬ測定を行い、次に第１の粒子線照射条件と第２の粒子線照射条件との粒子線照射量の差分を追加で照射し、この第１の粒子線照射条件の下、ＰＬ測定を行えば良い。
As another example, one sample of a silicon single crystal is prepared, and a particle beam is irradiated onto the sample under the first particle beam irradiation condition to perform PL measurement, and the G ray intensity G1 and the C ray intensity C1 are obtained. Next, the sample of the silicon single crystal irradiated with the particle beam under the first particle beam irradiation condition was measured for the particle beam irradiation amount under the first particle beam irradiation condition and the particle beam irradiation amount under the second particle beam irradiation condition. PL measurement is performed by additionally irradiating the difference, and G line intensity G2 and C line intensity C2 are obtained.
With such a method, since the same sample is used, the carbon concentration and the oxygen concentration are naturally the same, and the second proportionality constant α2 can be easily obtained by using the equation (B). This method is particularly effective when it is desired to increase the particle beam irradiation amount under the second particle beam irradiation condition more than the particle beam irradiation amount under the first particle beam irradiation condition.
On the contrary, when it is desired to reduce the particle beam irradiation amount of the second particle beam irradiation condition than the particle beam irradiation amount of the first particle beam irradiation condition, PL measurement is first performed under the second particle beam irradiation condition, Next, the difference in the particle beam irradiation amount between the first particle beam irradiation condition and the second particle beam irradiation condition may be additionally irradiated, and the PL measurement may be performed under the first particle beam irradiation condition.
これらの他には、過去のデータから炭素濃度と酸素濃度が同じであることが分かっているシリコン単結晶のサンプルを、第１の粒子線照射条件用と第２の粒子線照射条件用として各々用意することもできる。
あるいは、１枚のシリコン単結晶ウェーハ内において、互いに隣接する箇所から採取した２つのサンプルとすることもできる。
いずれの方法でも、第１の粒子線照射条件と第２の粒子線照射条件のサンプルの炭素濃度と酸素濃度は同一であるか、あるいは、同一とみなすことが出来る。したがって、式（Ｂ）を利用することができる。
そして式（Ｂ）に第１の比例定数α１、Ｇ線強度Ｇ１、Ｃ線強度Ｃ１、Ｇ線強度Ｇ２、Ｃ線強度Ｃ２を代入して、簡単に第２の比例定数α２を得ることができる。
In addition to these, a silicon single crystal sample whose carbon concentration and oxygen concentration are known to be the same from past data is used for the first particle beam irradiation condition and the second particle beam irradiation condition, respectively. You can also prepare.
Alternatively, it is also possible to use two samples taken from locations adjacent to each other in one silicon single crystal wafer.
In either method, the carbon concentration and the oxygen concentration of the sample under the first particle beam irradiation condition and the sample under the second particle beam irradiation condition are the same or can be regarded as the same. Therefore, the formula (B) can be used.
Then, by substituting the first proportional constant α1, the G ray intensity G1, the C ray intensity C1, the G ray intensity G2, and the C ray intensity C2 into the equation (B), the second proportional constant α2 can be easily obtained. ..
（工程３：第２の粒子線照射条件における炭素濃度測定）
第２の比例定数α２を代入した式（Ａ）を用いて、第２の粒子線照射条件における、シリコン単結晶中の炭素濃度の測定を行う。すなわち、測定するシリコン単結晶の、別に求めた酸素濃度と、第２の粒子線照射条件におけるＧ線強度Ｇ２やＣ線強度Ｃ２を式（Ａ）にさらに代入することで、シリコン単結晶中の炭素濃度を得ることができる。
(Step 3: Carbon concentration measurement under the second particle beam irradiation condition)
The carbon concentration in the silicon single crystal under the second particle beam irradiation condition is measured by using the expression (A) in which the second proportional constant α2 is substituted. That is, the oxygen concentration separately obtained for the silicon single crystal to be measured and the G-ray intensity G2 and C-ray intensity C2 under the second particle beam irradiation condition are further substituted into the formula (A) to obtain The carbon concentration can be obtained.
このような本発明の測定方法であれば、第１の粒子線照射条件から、より適切な測定条件である第２の粒子線照射条件へと最適化することにより、１×１０１３ａｔｏｍｓ／ｃｍ３以上という低濃度の炭素濃度を簡便に精度良く求めることが可能となる。 According to the measuring method of the present invention as described above, 1×10 13 atoms/cm 2 is obtained by optimizing the first particle beam irradiation condition to the second particle beam irradiation condition which is a more appropriate measuring condition. It is possible to easily and accurately obtain a carbon concentration as low as 3 or more.
以下、本発明の実施例及び比較例を示して本発明をより具体的に説明するが、本発明はこれらに限定されるものではない。
（実施例１）
上記したように、粒子線照射条件が、２ＭＶの加速電圧で電子線（ＥＢ）照射量が１×１０１５ｅｌｅｃｔｒｏｎｓ／ｃｍ２（第１の粒子線照射条件）で、ＰＬ測定時のサンプル温度が液体ヘリウム温度の場合における、式（Ａ）の第１の比例定数α１は４．４５×１０１４ａｔｏｍｓ／（ｃｍ３・ｐｐｍａ）と求められている。
Hereinafter, the present invention will be described more specifically by showing Examples and Comparative Examples of the present invention, but the present invention is not limited thereto.
(Example 1)
As described above, the particle beam irradiation condition is an acceleration voltage of 2 MV, the electron beam (EB) irradiation amount is 1×10 15 electrons/cm 2 (first particle beam irradiation condition), and the sample temperature during PL measurement is In the case of liquid helium temperature, the first proportionality constant α1 of the formula (A) is calculated to be 4.45×10 14 atoms/(cm 3 ·ppma).
次に、ＥＢ照射量を５×１０１５ｅｌｅｃｔｒｏｎｓ／ｃｍ２とした時（第２の粒子線照射条件）の第２の比例定数α２を求めるために、１枚のシリコンウェーハから、その中心部から同じ距離の位置から３つのサンプルを切り出した。これらの３つのサンプルは、互いに炭素濃度および酸素濃度が同一であるとみなせる。
その内の１つ目には第１の粒子線照射条件である１×１０１５ｅｌｅｃｔｒｏｎｓ／ｃｍ２の照射量で電子線を照射した。２つ目には第２の照射条件である５×１０１５ｅｌｅｃｔｒｏｎｓ／ｃｍ２の照射量で電子線を照射した。いずれも、電子線の加速電圧は２ＭＶとした。次に、それぞれのサンプルを液体ヘリウム温度でＰＬ測定を行い、第１の粒子線照射条件におけるＧ線強度Ｇ１およびＣ線強度Ｃ１と、第２の粒子線照射条件におけるＧ線強度Ｇ２およびＣ線強度Ｃ２を得た。
なお、３つ目については実施例１では使用せず、後述する比較例１で使用した。
Next, in order to obtain the second proportionality constant α2 when the EB irradiation dose is set to 5×10 15 electrons/cm 2 (second particle beam irradiation condition), from one silicon wafer, from the center portion thereof. Three samples were cut out at the same distance. These three samples can be regarded as having the same carbon concentration and oxygen concentration with each other.
The first of them was irradiated with an electron beam at a dose of 1×10 15 electrons/cm 2 , which is the first particle beam irradiation condition. The second was irradiated with an electron beam at a dose of 5×10 15 electrons/cm 2 , which is the second irradiation condition. In both cases, the electron beam acceleration voltage was set to 2 MV. Next, PL measurement was performed on each sample at the liquid helium temperature, and the G ray intensity G1 and C ray intensity C1 under the first particle beam irradiation condition and the G ray intensity G2 and C ray under the second particle beam irradiation condition were obtained. Strength C2 was obtained.
The third one was not used in Example 1 but was used in Comparative Example 1 described later.
上記の２つのサンプルに対するＰＬ測定を、炭素濃度、酸素濃度が異なると予想される１９水準のサンプルに対して行い、｛（Ｇ線強度Ｇ１／Ｃ線強度Ｃ１）／（Ｇ線強度Ｇ２／Ｃ線強度Ｃ２）｝の平均値を求めたところ、１．３１７であった。
図２に（Ｇ線強度Ｇ１／Ｃ線強度Ｃ１）と（Ｇ線強度Ｇ２／Ｃ線強度Ｃ２）の関係をプロットで示す。なお、参考として、図２に傾き１のグラフ（（Ｇ線強度Ｇ１／Ｃ線強度Ｃ１）＝（Ｇ線強度Ｇ２／Ｃ線強度Ｃ２））を実線で引いている。
従って、第２の比例定数α２は、第１の比例定数α１と上記平均値を式（Ｂ）に代入し、即ち、４．４５×１０１４×１．３１７により、５．８６×１０１４ａｔｏｍｓ／（ｃｍ３・ｐｐｍａ）と求まった。
The PL measurement for the above two samples was performed on 19 levels of samples, which are expected to have different carbon and oxygen concentrations, and {(G line intensity G1/C line intensity C1)/(G line intensity G2/C The average value of the line intensities C2)} was 1.317.
FIG. 2 is a plot showing the relationship between (G line intensity G1/C line intensity C1) and (G line intensity G2/C line intensity C2). For reference, a graph with a slope of 1 ((G line intensity G1/C line intensity C1)=(G line intensity G2/C line intensity C2)) is drawn by a solid line in FIG.
Therefore, the second proportionality constant α2 is obtained by substituting the first proportionality constant α1 and the average value into the formula (B), that is, 4.45×10 14 ×1.317, that is, 5.86×10 14 atoms. /(Cm 3 ·ppma) was obtained.
次に、上記１９水準のサンプルについて、別に求めた酸素濃度と、Ｇ線強度Ｇ２、Ｃ線強度Ｃ２を、上記第２の比例定数α２を代入した式（Ａ）に対して代入した。これにより、第２の粒子線照射条件における炭素濃度を求めることができた。
ここで、同様にして第１の粒子線照射条件（第１の比例定数α１）における炭素濃度も求め、該第１の粒子線照射条件から求めた炭素濃度と、第２の粒子線照射条件から求めた炭素濃度を図３にプロットで示し、比較した。なお、参考として、傾き１のグラフ（第１の粒子線照射条件から求めた炭素濃度＝第２の粒子線照射条件から求めた炭素濃度）を実線で引いている。図３に示すように、両者は非常に良く一致した。すなわち、第２の比例定数α２が、特願２０１８−００３４２７と同様にして煩雑な作業を行って求めた第１の比例定数α１と同程度に高精度であることが分かる。しかも、第２の比例定数α２を求めるにあたって、特願２０１８−００３４２７のような煩雑な作業が必要ないため、簡単である。
Next, with respect to the above 19-level samples, the oxygen concentration, G line intensity G2, and C line intensity C2, which were separately obtained, were substituted into the equation (A) into which the second proportionality constant α2 was substituted. Thereby, the carbon concentration under the second particle beam irradiation condition could be obtained.
Here, similarly, the carbon concentration under the first particle beam irradiation condition (first proportionality constant α1) is also obtained, and the carbon concentration obtained from the first particle beam irradiation condition and the second particle beam irradiation condition are obtained. The obtained carbon concentration is shown in a plot in FIG. 3 for comparison. For reference, a graph with a slope of 1 (carbon concentration obtained from the first particle beam irradiation condition=carbon concentration obtained from the second particle beam irradiation condition) is drawn by a solid line. As shown in FIG. 3, the two agree very well. That is, it is understood that the second proportionality constant α2 is as accurate as the first proportionality constant α1 obtained by performing the complicated work in the same manner as in Japanese Patent Application No. 2018-003427. In addition, it is easy to obtain the second proportionality constant α2, since complicated work such as that in Japanese Patent Application No. 2018-003427 is not required.
（実施例２）
実施例１において、第１の粒子線照射条件（加速電圧２ＭＶ、照射量１×１０１５ｅｌｅｃｔｒｏｎｓ／ｃｍ２）で電子線を照射して液体ヘリウム温度にてＰＬ測定（Ｇ線強度Ｇ１、Ｃ線強度Ｃ１）を行ったサンプルに対して、加速電圧２ＭＶにて４×１０１５ｅｌｅｃｔｒｏｎｓ／ｃｍ２の電子線照射を追加して行い、合わせて５×１０１５ｅｌｅｃｔｒｏｎｓ／ｃｍ２の電子線照射を行ったサンプルを用意した。これの液体ヘリウム温度におけるＧ線強度Ｇ２およびＣ線強度Ｃ２を求めた。
(Example 2)
In Example 1, an electron beam was irradiated under the first particle beam irradiation condition (accelerating voltage 2 MV, irradiation amount 1×10 15 electrons/cm 2 ) and PL measurement was performed at a liquid helium temperature (G-ray intensity G1, C-ray). The sample subjected to the intensity C1) was additionally irradiated with an electron beam of 4×10 15 electrons/cm 2 at an accelerating voltage of 2 MV, and a total of 5×10 15 electrons/cm 2 was irradiated. Prepared samples. The G line intensity G2 and the C line intensity C2 at the liquid helium temperature were obtained.
上記１９水準のサンプルの、（Ｇ線強度Ｇ１／Ｃ線強度Ｃ１）／（Ｇ線強度Ｇ２／Ｃ線強度Ｃ２）の平均値を求めたところ、１．３１７であった。
従って、第２の比例定数α２は、第１の比例定数α１と上記平均値を式（Ｂ）に代入し、即ち、４．４５×１０１４×１．３１７により、５．８６×１０１４ａｔｏｍｓ／（ｃｍ３・ｐｐｍａ）と求まった。このように実施例１と同様の数値になった。
The average value of (G-line intensity G1/C-line intensity C1)/(G-line intensity G2/C-line intensity C2) of the above 19-level samples was 1.317.
Therefore, the second proportionality constant α2 is obtained by substituting the first proportionality constant α1 and the average value into the formula (B), that is, 4.45×10 14 ×1.317, that is, 5.86×10 14 atoms. /(Cm 3 ·ppma) was obtained. In this way, the numerical values were the same as in Example 1.
次に、上記１９水準のサンプルについて、第１の粒子線照射条件から求めた炭素濃度（第１の比例定数α１を代入した式（Ａ）使用）と、第２の粒子線照射条件から求めた炭素濃度（上記のようにして求めた第２の比例定数α２を代入した式（Ａ）使用）を比較したところ、実施例１と同様に図３のような結果となり、両者は非常に良く一致した。 Next, for the above 19-level samples, the carbon concentration obtained from the first particle beam irradiation condition (using the equation (A) in which the first proportionality constant α1 was substituted) and the second particle beam irradiation condition were obtained. Comparison of the carbon concentrations (using the formula (A) in which the second proportionality constant α2 obtained as described above was substituted) resulted in the results shown in FIG. 3 as in Example 1, and the two agree very well. did.
（比較例１）
実施例１で切り出したサンプルの内、何も処理をしていない残りの１つのサンプル（すなわち、１つ×１９水準分）を用いて、これをさらに３分割して、それぞれの炭素濃度をＳＩＭＳ法により、酸素濃度をＦＴ−ＩＲ法により求めた。その後、加速電圧２ＭＶにて５×１０１５ｅｌｅｃｔｒｏｎｓ／ｃｍ２の電子線照射を行った。次に液体ヘリウム温度にてＰＬ測定を行い、Ｇ線強度およびＣ線強度を得た。
(Comparative Example 1)
Of the samples cut out in Example 1, the remaining one sample (that is, 1×19 levels) that had not been subjected to any treatment was further divided into three, and the carbon concentration of each was calculated by SIMS. Oxygen concentration was determined by the FT-IR method. Then, electron beam irradiation of 5×10 15 electrons/cm 2 was performed at an acceleration voltage of 2 MV. Next, PL measurement was performed at a liquid helium temperature to obtain G line intensity and C line intensity.
それぞれのサンプルにおいて、炭素濃度、酸素濃度、Ｇ線強度、Ｃ線強度を、式（Ａ）
に代入して比例定数を求めた。これの１９水準のサンプルの平均値は５．８６×１０１４ａｔｏｍｓ／（ｃｍ３・ｐｐｍａ）であった（比例定数βとする）。図４に各サンプルから求めた比例定数βと炭素濃度との関係を示す。この数値は、実施例１および実施例２の第２の比例定数α２と同一の値であるものの、これを得るために各サンプルの炭素濃度、酸素濃度を求めたために、多大なる時間が掛かった。
For each sample, the carbon concentration, oxygen concentration, G-ray intensity, and C-ray intensity were calculated using the formula (A)
To obtain the constant of proportionality. The average value of 19 level samples was 5.86×10 14 atoms/(cm 3 ·ppma) (proportional constant β). FIG. 4 shows the relationship between the proportionality constant β obtained from each sample and the carbon concentration. Although this numerical value is the same value as the second proportionality constant α2 of Example 1 and Example 2, it took a lot of time because the carbon concentration and oxygen concentration of each sample were obtained in order to obtain this value. ..
そして、上記１９水準のサンプルについて、第１の粒子線照射条件から求めた炭素濃度（第１の比例定数α１を代入した式（Ａ）使用）と、第２の粒子線照射条件から求めた炭素濃度（上記のようにして求めた第２の粒子線照射条件における比例定数βを代入した式（Ａ）使用）を比較したところ、両者は非常に良く一致した。しかしながら、上述したように、第２の粒子線照射条件における比例定数βを求めるために多大な時間がかかったため、測定全体として時間が多大になってしまった。 Then, for the above 19-level samples, the carbon concentration obtained from the first particle beam irradiation condition (using the formula (A) in which the first proportional constant α1 was substituted) and the carbon concentration obtained from the second particle beam irradiation condition When the concentrations (using the formula (A) in which the proportional constant β under the second particle beam irradiation condition obtained as described above is substituted) were compared, the two were in very good agreement. However, as described above, it takes a lot of time to obtain the proportional constant β under the second particle beam irradiation condition, so that the whole measurement takes a lot of time.
（実施例３）
シリコン単結晶から採取したサンプル（直径３００ｍｍ、ＭＣＺ結晶、固化率＝２０％の位置）を用意し、実施例１と同様の第１の粒子線照射条件の下、液体ヘリウム温度にてＰＬ測定を行った。この結果、第１の粒子線照射条件ではＣ線は十分なピーク強度が得られたが、Ｇ線ピークが弱く、炭素濃度を定量できなかった。
このサンプルに隣接するサンプルを用意し、これに実施例１と同様の第２の粒子線照射条件でＥＢ照射を行い、液体ヘリウム温度でＰＬ測定を行った。この結果、Ｇ線、Ｃ線ともに十分なピーク強度を得られた。
そこで、実施例１で求めた、第２の粒子線照射条件における第２の比例定数α２（５．８６×１０１４）を代入した式（Ａ）を用い、別に求めた酸素濃度、先に求めた第２の粒子線照射条件のＰＬ測定でのＧ線強度、Ｃ線強度を代入することによって、第２の粒子線照射条件における炭素濃度を求めたところ、１．０×１０１３ａｔｏｍｓ／ｃｍ３と求めることが出来た。
(Example 3)
A sample (diameter 300 mm, MCZ crystal, solidification rate=20% position) collected from a silicon single crystal was prepared, and PL measurement was performed at the liquid helium temperature under the same first particle beam irradiation conditions as in Example 1. went. As a result, under the first particle beam irradiation condition, a sufficient C-ray peak intensity was obtained, but the G-ray peak was weak and the carbon concentration could not be quantified.
A sample adjacent to this sample was prepared, subjected to EB irradiation under the same second particle beam irradiation conditions as in Example 1, and PL measurement was performed at the liquid helium temperature. As a result, sufficient peak intensities were obtained for both G and C lines.
Therefore, using the formula (A) in which the second proportionality constant α2 (5.86×10 14 ) under the second particle beam irradiation condition obtained in Example 1 is substituted, the oxygen concentration obtained separately is obtained previously. When the carbon concentration under the second particle beam irradiation condition was obtained by substituting the G ray intensity and the C ray intensity in the PL measurement under the second particle beam irradiation condition, it was 1.0×10 13 atoms/cm 2. I was able to ask for 3 .
（実施例４）
シリコン単結晶から採取したサンプル（直径３００ｍｍ、ＭＣＺ結晶、固化率＝２０％の位置）（実施例３と同様のサンプル）を用意し、実施例１と同様の第１の粒子線照射条件の下、液体ヘリウム温度にてＰＬ測定を行った。この結果、第１の粒子線照射条件ではＣ線は十分なピーク強度が得られたが、Ｇ線ピークが弱く、炭素濃度を定量できなかった。
このサンプルについて、第１の粒子線照射条件でＥＢ照射を行ったサンプルそのものに、追加で加速電圧２ＭＶにて４×１０１５ｅｌｅｃｔｒｏｎｓ／ｃｍ２の電子線照射を行い、合わせて５×１０１５ｅｌｅｃｔｒｏｎｓ／ｃｍ２の電子線照射を行ったサンプルを用意した。これを、液体ヘリウム温度でＰＬ測定を行った。この結果、Ｇ線、Ｃ線ともに十分なピーク強度を得られた。
そこで、実施例２で求めた第２の粒子線照射条件における第２の比例定数α２（５．８６×１０１４）を代入した式（Ａ）を用い、別に求めた酸素濃度、先に求めた第２の粒子線照射条件のＰＬ測定でのＧ線強度、Ｃ線強度を代入することによって、第２の粒子線照射条件における炭素濃度を求めたところ、１．０×１０１３ａｔｏｍｓ／ｃｍ３と求めることが出来た。
(Example 4)
A sample (diameter 300 mm, MCZ crystal, solidification rate=20% position) (sample similar to that of Example 3) prepared from a silicon single crystal was prepared, and under the same first particle beam irradiation condition as that of Example 1. PL measurement was performed at the liquid helium temperature. As a result, under the first particle beam irradiation condition, a sufficient C-ray peak intensity was obtained, but the G-ray peak was weak and the carbon concentration could not be quantified.
About this sample, electron beam irradiation of 4×10 15 electrons/cm 2 was additionally performed at an accelerating voltage of 2 MV to the sample itself that was EB-irradiated under the first particle beam irradiation condition, and a total of 5×10 15 electrons was irradiated. A sample irradiated with an electron beam of /cm 2 was prepared. This was subjected to PL measurement at a liquid helium temperature. As a result, sufficient peak intensities were obtained for both G and C lines.
Therefore, using the formula (A) in which the second proportionality constant α2 (5.86×10 14 ) under the second particle beam irradiation condition obtained in Example 2 is substituted, the oxygen concentration obtained separately is obtained previously. When the carbon concentration under the second particle beam irradiation condition was obtained by substituting the G ray intensity and the C ray intensity in the PL measurement under the second particle beam irradiation condition, it was 1.0×10 13 atoms/cm 3. I was able to ask.
（比較例２）
シリコン単結晶から採取したサンプル（直径３００ｍｍ、ＭＣＺ結晶、固化率＝２０％の位置）（実施例３と同様のサンプル）を用意し、実施例１と同様の第１の粒子線照射条件の下、液体ヘリウム温度にてＰＬ測定を行った。この結果、第１の粒子線照射条件ではＣ線は十分なピーク強度が得られたが、Ｇ線ピークが弱く、炭素濃度を定量できなかった。
このサンプルに隣接するサンプルを用意し、これに比較例１と同様の粒子線照射条件でＥＢ照射を行い、液体ヘリウム温度でＰＬ測定を行った。この結果、Ｇ線、Ｃ線ともに十分なピーク強度を得られた。
そこで、比較例１で多大な時間をかけて求めた比例定数β（５．８６×１０１４）を代入した式（Ａ）を用い、別に求めた酸素濃度、先に求めた比較例１と同様の粒子線照射条件のＰＬ測定でのＧ線強度、Ｃ線強度を代入することによって、比較例１と同様の粒子線照射条件における炭素濃度を求めたところ、１．０×１０１３ａｔｏｍｓ／ｃｍ３と求めることが出来た。
(Comparative example 2)
A sample (diameter 300 mm, MCZ crystal, solidification rate=20% position) (sample similar to that of Example 3) prepared from a silicon single crystal was prepared, and under the same first particle beam irradiation condition as that of Example 1. PL measurement was performed at the liquid helium temperature. As a result, under the first particle beam irradiation condition, a sufficient C-ray peak intensity was obtained, but the G-ray peak was weak and the carbon concentration could not be quantified.
A sample adjacent to this sample was prepared, subjected to EB irradiation under the same particle beam irradiation conditions as in Comparative Example 1, and PL measurement was performed at the liquid helium temperature. As a result, sufficient peak intensities were obtained for both G and C lines.
Therefore, using the formula (A) in which the proportional constant β (5.86×10 14 ) obtained in Comparative Example 1 over a long time is substituted, the oxygen concentration obtained separately, the same as in Comparative Example 1 obtained earlier. When the carbon concentration under the same particle beam irradiation condition as in Comparative Example 1 was obtained by substituting the G ray intensity and the C ray intensity in the PL measurement under the particle beam irradiation condition of No. 1, it was 1.0×10 13 atoms/cm 2. I was able to ask for 3 .
このように、本発明による実施例１、２や実施例３、４は、各々、特願２０１８−００３４２７の方法による比較例１や比較例２と少なくとも同程度に高精度で炭素濃度を測定することができた。また、第２の粒子線照射条件を調整すれば、より低濃度の炭素濃度も測定可能となる。しかも、実施例１−４では、比較例１−２において行ったような煩雑な作業をなくし、従来法よりも時間をかけずに簡便に測定を行うことができた。 As described above, in Examples 1 and 2 and Examples 3 and 4 according to the present invention, the carbon concentration is measured with at least as high precision as Comparative Example 1 and Comparative Example 2 according to the method of Japanese Patent Application No. 2018-003427. I was able to. Moreover, if the second particle beam irradiation condition is adjusted, a lower carbon concentration can be measured. Moreover, in Example 1-4, the complicated work as in Comparative Example 1-2 was eliminated, and the measurement could be easily performed in less time than the conventional method.
なお、本発明は、上記実施形態に限定されるものではない。上記実施形態は、例示であり、本発明の特許請求の範囲に記載された技術的思想と実質的に同一な構成を有し、同様な作用効果を奏するものは、いかなるものであっても本発明の技術的範囲に包含される。 The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, has substantially the same configuration as the technical idea described in the scope of the claims of the present invention, and has the same operational effect It is included in the technical scope of the invention.
Claims (6)
前記シリコン単結晶中の炭素濃度を、下記式
炭素濃度＝比例定数×酸素濃度×（Ｇ線強度／Ｃ線強度）…（Ａ）
を用いて測定するとき、
予め、第１の粒子線照射条件における、前記式（Ａ）の前記比例定数である第１の比例定数α１を求めておき、
次に、シリコン単結晶のサンプルを用意し、
前記第１の比例定数α１を求めたときと同じ前記第１の粒子線照射条件でのＰＬ測定またはＣＬ測定を行い、Ｇ線強度Ｇ１およびＣ線強度Ｃ１を求め、かつ、
前記第１の粒子線照射条件とは異なる第２の粒子線照射条件でのＰＬ測定またはＣＬ測定を行い、Ｇ線強度Ｇ２およびＣ線強度Ｃ２を求め、
その後、前記第２の粒子線照射条件における、前記式（Ａ）の前記比例定数である第２の比例定数α２を、下記式
比例定数α２＝比例定数α１×｛（Ｇ線強度Ｇ１／Ｃ線強度Ｃ１）／（Ｇ線強度Ｇ２／Ｃ線強度Ｃ２）｝…（Ｂ）
から決定し、
該決定した比例定数α２を代入した前記式（Ａ）を用いて、前記第２の粒子線照射条件における、前記シリコン単結晶中の炭素濃度の測定を行うことを特徴とする炭素濃度測定方法。 Carbon concentration measurement for measuring the carbon concentration in the silicon single crystal by using the G and C ray intensities obtained by PL measurement or CL measurement of the silicon single crystal irradiated with the particle beam and the oxygen concentration obtained separately Method,
The carbon concentration in the silicon single crystal is calculated by the following formula: carbon concentration=proportional constant×oxygen concentration×(G line intensity/C line intensity) (A)
When measuring with
In advance, the first proportionality constant α1 which is the proportionality constant of the formula (A) under the first particle beam irradiation condition is obtained,
Next, prepare a sample of silicon single crystal,
PL measurement or CL measurement under the same first particle beam irradiation condition as when the first proportionality constant α1 is obtained is performed to obtain a G ray intensity G1 and a C ray intensity C1, and
PL measurement or CL measurement under a second particle beam irradiation condition different from the first particle beam irradiation condition is performed to obtain a G ray intensity G2 and a C ray intensity C2,
Then, under the second particle beam irradiation condition, the second proportional constant α2, which is the proportional constant of the formula (A), is calculated by the following formula: proportional constant α2=proportional constant α1×{(G ray intensity G1/C ray Intensity C1)/(G line intensity G2/C line intensity C2)}... (B)
Decided from
A carbon concentration measuring method, characterized in that the carbon concentration in the silicon single crystal under the second particle beam irradiation condition is measured by using the formula (A) in which the determined proportionality constant α2 is substituted.
１枚のシリコン単結晶ウェーハから、該シリコン単結晶ウェーハの中心から同じ距離の位置から採取した２つのウェーハ片を用意し、
前記第１の粒子線照射条件でのＰＬ測定またはＣＬ測定を前記２つのウェーハ片のうちの一方で行い、
前記第２の粒子線照射条件でのＰＬ測定またはＣＬ測定を他方で行うことを特徴とする請求項１または請求項２に記載の炭素濃度測定方法。 As a sample of the silicon single crystal,
Two wafer pieces taken from one silicon single crystal wafer at the same distance from the center of the silicon single crystal wafer are prepared,
PL measurement or CL measurement under the first particle beam irradiation condition is performed on one of the two wafer pieces,
The carbon concentration measuring method according to claim 1 or 2, wherein PL measurement or CL measurement under the second particle beam irradiation condition is performed on the other side.
前記第１の粒子線照射条件で粒子線を照射した前記シリコン単結晶のサンプルに、前記第１の粒子線照射条件の粒子線照射量と第２の粒子線照射条件の粒子線照射量の差分を追加照射して行うことを特徴とする請求項１または請求項２に記載の炭素濃度測定方法。 As PL measurement or CL measurement under the second particle beam irradiation condition,
The difference between the particle beam irradiation amount under the first particle beam irradiation condition and the particle beam irradiation amount under the second particle beam irradiation condition for the sample of the silicon single crystal irradiated with the particle beam under the first particle beam irradiation condition. The method for measuring carbon concentration according to claim 1 or 2, further comprising:
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